This invention relates to input devices for a computer and more specifically to a type of analog input device known as a mouse.
It is known in the art to enter information into a computer using an analog input device known as a mouse. A mouse is particularly useful for entering positional information into computers. A typical mouse has the shape of a rectangular prism having dimensions of about 1.5 by 1.0 by 2.5 inches and rests on a surface, e.g. a table top. A person using the mouse moves the mouse relative to the surface. Transducers in the mouse detect and provide electrical signals indicative of this movement. A host computer receives these signals and responds appropriately. These signals can be used by a computer to move a cursor around on a CRT screen so as to enable a user to determine where on the screen text is to be entered. In addition, a mouse can be used to draw images on the screen.
Some prior art mouse devices use electro-mechanical transducers. For example, referring to FIG. 1, on the bottom of a mouse 10 is a rotatably mounted sphere 12. As mouse 10 is moved across surface 14, sphere 12 rotates. Sphere 12 is mounted so as to push against a shaft 16. Therefore, as mouse 10 moves in a first direction, sphere 12 rotates causing shaft 16 to rotate. This rotation is detected with an electro-mechanical transducer such as shaft encoder 18. A second shaft and shaft encoder (not shown) are also included in mouse 10 to detect motion in a second direction perpendicular to the first direction.
Another prior art mouse is mouse 20 (FIG. 2) which rests on a surface 22. Surface 22 has formed thereon a set of lines 24 of a first color and a set of lines 26 perpendicular to lines 24 of a second color. An opto-electrical transducer 28 is sensitive to light of the first color but not the second. As mouse 20 passes over lines 24, transducer 28 provides electrical signals indicative of motion in the direction indicated by arrow A. Similarly, as mouse 20 passes over lines 26, a second opto-electrical transducer 30 provides signals indicative of motion in the direction indicated by arrow B.
It is also known in the art to provide a data input device known as a digitizing pad. One example of a digitizing pad is bit pad 32 illustrated in FIG. 3. Bit pad 32 includes a surface having a grid of horizontal wires 34 and vertical wires 36, each wire being electrically insulated from the others. A voltage is sequentially applied to each wire within wires 34 and 36. A stylus 38 is placed on bit pad 32 by a user. Stylus 38 includes a voltage sensing device 40. When voltage sensing device 40 detects the presence of a strong electric field, the position of sensing device 40 is determined, since it is known that device 40 only detects strong electric fields when near the wire receiving the voltage.
Although mouse devices provide signals to a computer which accurately indicate movement of the mouse, Applicant has found that a mouse shaped like a rectangular prism is difficult to draw with. This is true in part because the dexterity in an average person's thumb and opposing forefinger, which in general is the most dexterous part of the hand, cannot be exploited well in a typical prism-shaped mouse. While stylus-shaped devices are easier to draw with, the time spent finding a stylus, picking it up, putting it down, and picking it up again represents an inconvenience.